The use of bioassays to determine reduction equivalent doses delivered by UV reactors is recognized as an effective measure of UV disinfection systems. Low pressure (LP) UV delivered in controlled collimated beam systems provides dose response curves which are then compared against reactor performance to quantify the delivered dose. It is recognized that the appropriateness of monochromatic LP dose curves for validating polychromatic medium pressure depends on knowledge of the action spectra of the bioassay surrogate and the target pathogen. Further complicating the relationship between REDs generated during validation and effective dose delivered by a medium pressure UV system at an installation is the absorbance spectrum of the validation water vs that at the utility. Other factors that affect the dependability of bioassay results for medium pressure systems include quartz sleeve absorbance spectra and lamp spectral output. These latter factors can be resolved or corrected for, but not without knowledge of the action spectra of the microorganisms in question. Existing characterization of the action spectra of pathogens and bioassay surrogates is limited, and ranges from two published (Rauth, 1965; Mamane-Gravetz, et al. 2005) and three unpublished studies on the commonly used surrogate, coliphage MS2, to one published study on Cryptosporidium (Linden et al., 2001) and adenovirus (Malley et al, 2004), to no information on several surrogates. Further, the methodologies used to irradiate microbes with distinct wavelengths have varied across studies. Data reported as representative of the relative inactivations of given wavelengths may actually represent the inactivations achieved by a range of wavelengths produced by a polychromatic lamp filtered by wide-width bandpass filters.
Proceedings Title: IOA & IUVA 2013 World Congress & Exhibition
Conference Dates: September 22-26, 2013
Conference Location: Las Vegas, NV
Pub Type: Conferences
Action Spectra, Ultraviolet Light, Water Disinfection, Medium Pressure UV, Low Pressure UV, Cryptosporidium, Giardia, Adenovirus Type 2